Such a coating dispersion is known from EP-A-589529. The dispersion described in this patent contains electrically conductive particles in a dispersant described in EP-A-589529. The particles comprise a binder, stabilized by a non-ionic stabilizer, and an electrically conductive polymer. The dispersion of electrically conductive particles is obtained by polymerizing monomers into an electrically conductive polymer in the presence of a dispersion of binder particles stabilised by means of a non-ionic stabilizer. The binder is a thermoplastic polymer. The dispersion of electrically conductive particles described in EP-A-589529 is characterised by a homogeneous particle size. Moreover, the electrically conductive polymer is homogeneously distributed over the electrically conductive particles. The stability of the dispersion of electrically conductive particles described in EP-A 589529 is realized because the electrically conductive particles also contain a non-ionic stabilizer. Such a dispersion has been found to be very stable, even when it contains ionic compounds.
In 1981 already Mengoli et al. suggested in J. Appl. Polym. Sci. 1981, 26, 4247-4257, that conductive polymers could be used to protect metals against corrosion. However, the first positive results were obtained by Thompson only 10 years later, using a coating based on polyaniline; they were reported in Los Alamos National Report LA-UR-92-360. It was found that soft steel was protected against corrosion in salt and acid environments, even in areas where scratches were made in the coating.
The drawback of the dispersion known from EP-A-589529, however, is that the anticorrosive effect of a coating based thereon is considerably less in a damp or wet environment than in a dry environment. As metal generally corrodes in a damp environment, this can be seen as a major drawback for the application in anticorrosive paint.